Synthesis Of Molybdate Enhanced Anodic Cobalt Oxide Composite Catalyst For Electrocatalytic Water Splitting

There has been a significant improvement in the demand of energy as a result of technological advances.However,emissions from the use of traditional fossil fuels have become a source of pollution,which is responsible for global warming,climate change and other environmental problems.Thus,it is necessary to develop clean energy,such as hydrogen energy,to lessen the dependence on fossil fuels.Technique of electrocatalyzing water via.hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)is the most environmentally-friendly method of large-scale production of hydrogen.Some of noble metals and their compounds have proven to be the most active catalyst toward electrolysis of water,but it hardly comes into extensive use due to its expensive cost.Over the last decade,myriad financial support has been invested in the investigation of non-noble metal catalysts.However,the activities of these catalysts were still far from commercial use.In this work,Co3O4/Co(ACO)was synthesized via a facile anode oxidation technique.Then,molybdate was deposited on ACO by chemical bath deposition in order to promote the catalytic activity.For starters,ACOs with different morphologies and different contents of Co3O4 were fabricated by changing anodic oxidation times,anodic oxidation potentials and concentration of ammonium fluoride.HER tests revealed that the HER activity of ACO was superior to that of Co and Co3O4.In addition,experimental results also indicated that micro morphology and content of Co3O4 had little effect on HER performance of ACOs.Further analysis showed that the enhanced HER activity of ACO was caused by the electronic effect between Co and Co3O4,namely,in ACO,Co is more likely to absorb electrons from Co3O4,resulting in a phenomenon of electron transfer.OER tests revealed that synthesis conditions played a key role in OER performance of ACO.Generally speaking,the longer anodic oxidation time and higher anodic oxidation potential,the better OER activity.ACO based catalysts saw a significantly increase in HER performance after depositing molybdate,which revealed that the synergistic effect between molybdate and ACO can benefit the HER activities of catalysts.The as-prepared CoMoO4/ACO-60 showed an excellent HER performance with an overpotential of 78 mV at the current density of-10 mA/cm2 in 1M KOH.In addition,ACOs of different morphologies were prepared in order to get an insight into the role of morphologies of matrix in HER ability.Studies suggested that the tubular structure ACO allows the deposited molybdate to avoid aggregation efficiently,which enabled catalysts to possess a large active surface area and therefore more active sites can take part in HER reaction.